Keying arrangement for radio transmitters



q- 24, 1940- E. STUTIUS 2,215,800

KEYING ARRANGEMENT FOR RADIO TRANSMITTERS Filed Deb. 17. 1937 2 Sheets-Sheet l Q V A I i /sec fifq] I fizvezzzar: 2 [HZ/7.90MB

Sept. 24, 1940.

E. s'ruTlus KEYING ARRANGEMENT FOR RADIO TRANSMITTERS 2 Sheets-Sheet 2 Filed Dec. 17; 1937 I l I I I I I I I I I I I l I I I I I I I I I Patented Sept. 24, '1940 UNITED STATES KEYING ARRANGEMENIFOR RADIO TRANSMIT TERS Erich Stutius, Berlin, Germany, assignor to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof,

Germany, a company Application December 17, 1937, Serial No. 180,387 In Germany March 11, 1937 4 Claims.

Thepresent invention relates to an arrangement for keying high irequency transmitters, and permits such equipments to be continuously keyed in a constant rhythm in accordance with 5 telegraph signals in a very simple manner without employing mechanically actuated means. This new arrangement is particularly advantageously employed for keyirm radio beacons adapted to indicate position and direction to ships, aircraft and other vehicles.

It is frequently desired in connection with high frequency transmitters to obtain keying, a modulation tone, for example, in a continuously constant rhythm, which may be in order. of l to 10 cycles per second, for instance. The signal interval is fixedly related to the gap interval, that is to say, the signal intervals are either longer or shorter than the gaps.

The previously known keying devices of this type have used rotational interrupters, i. e. cam

discs which actuate the keying contacts in a predetermined rhythm. However, this method involves several disadvantages. First of all, considerable expenditure is required on account of the fact, that motor driven means are necessary;

On the other hand, the tendency to failures involved in devices of this kind introduces considerable lack of reliability in operation. The requirement with respect to the necessity of continuous constancy of the keying frequency is a furtherdrawback, as these devices must operate independently of voltage variations, for instance, when electromotors are used. I Finally, it is frequently required in. suchhig frequency transmitters to secure a very quick change over from one keying frequency to another, e. g. by actuating a switch. The sole possibility for realizing this requirement in devices operating with rotational cam discs is the availability of a considerable number of different and arbitrarily interchangeable discs, or a number of simultaneously rotating discs and a corresponding number of key contacts which are optionally switched in circuit by means of a switching device. The first mentioned arrangement involves the disadvantage that a changeover from one keying frequency to another cannot be performed solely by operating a switching device, while the keying equipment is essentially complicated on employing the last mentioned method. The present invention proposes a new keying arrangement according to which the aforesaid disadvantages are obviated, and which permits a changeover from one keying frequency to an- 5 other in a most simple manner. This is obtained by effecting the keying by means of a relay interrupter, the frequency and signal-to-gap ratio of which is given by the timing of the relays forming part of the interrupter. A changeover from 60 one keying frequency to other such frequencies ing the switch S.

A, the relay I is energized over: battery B, resist- 40' is attained by the provision of further timed relays, which are rendered effective or ineffective by a simple switch. Thisarrangement permits the keying device to be dimensioned s0 as-to provide a great number of different keying fre- 5 quencies and signal-to-gap ratios and to be adjusted to the desired keying signals merely by actuating a single switch. This switch, for instance, may simultaneously be used for creating a changeover with respect of the modulation ire- 10 quency to be keyed. The operation reliability of this new keying arrangement is essentially superior over arrangements of this type known in the past, as the novel device completely omits rotational means, andon account of the fact that 15 the relays may be adjusted to operate independently of temperature influences or voltage variations. v

The invention will be more readily understood from the following description in conjunction go with the attached drawings, in which:

Fig. 1 diagrammatically illustrates two diiferent keying rhythms; Fig. 2 schematically demonstrates a relay interrupter according to the invention, while Fig. 3 shows a schematically circuit 25 arrangement of a radio beacon system for landing aeroplanes and which employs the keying arrangement according to the invention.

Referring to Fig. 1, there is shown at a and 1: two examples of keying rhythms within a one 30 seconds interval. The signal and the gap intervals are selected according to a given ration.

The Fig. 2 shows'one embodiment of the keying arrangement of theinvention. Two relays I and II are provided for one keying frequency and 35 these relays may be supplemented by a third relay III for obtaining a second keying frequency. The latter relay is to be connected in circuit by clos- On closing the starting switchance WI, and the contacts 3 and 2. It closes its contact I and establishes a circuit for the relay II over: battery B, resistance W2, thus causing the slow operating relay to attract and to open its contact 2, whereby the circuit for the relay I 45 is interrupted. This relay releases after the elapse of agive'n period in which moment it opens its contact I included in the circuit of the relay II. This relay is de-energized and caused to release after a given period with the result that its contact 2 is again closed. The relay I is re-energized and the above described operating cycle again commences. In cases that the switch S is closed, the relay III is included in the keying operation, and its timing contributes in an additional sense so as to reduce the keying frequency. The contact 2' likewise controlled by the relay II and which is provided in the keying circuit serves as keying switch. The release of the individual relays forming part of the interrupter arrangeo ment "is adjusted in any known manner by the provision of series or parallelresistors, e. g. the

resistances WI and W2 shown in Fig. 2.. The periods of make and breakare thereby adjusted so as to obtain a given signal-to-gap'ratid.

The present invention is by no means limited to the aforesaid embodiment, on the contrary. it will be possible to provide a number of further relays which are either permanently included or intermittently rendered operative orinoper'ative in order to vary keying frequency. The above described new keying arrangemen is particularly suitable for the keying of direction finding systems, which are adapted to effect position indications to aircrafts and the like. One example for practically applying this keying arrangement is hereinafter described. It may be assumed that a directional signal transmitter of the type utilized in connection with radio beacons for landing airplanes. is employed and that this device is adapted to transmit to the pilot the moment when the landing is to be commenced. The principal circuit arrangement of such a device, is demonstrated in Fig.3. The high frequency transmitter which by aid of the horizontal antenna E produces a wall-shaped and upwardly directed radiation is modulated with a predetermined modulation tone of 700 or 1700 cycles per second, for instance, and keyed in a dash rhythm having a given signal to-gap ratio. The modulation frequency is produced by a low frequency generator, so arranged that either of the modulation frequencies 700 or 1700 cycles per second may be employed merely by actuating the make and break switch SI, which opens or closes the circuit in which the condenser C is included. The keyingof the transmitter is effected by virtue of the arrangement proposed according to the invention in such a manner that the low frequency generator is connected to'or disconnec from the high frequency-transmitter in a rhythm which corresponds to the signals to be keyed.

The portion of Fig. 3 within the dotted lines exactly corresponds to the circuit arrangement of Fig. 2, although shown having its contact in their actual positions relative to their corresponding relay windings.

other by adding or omitting the relay III in the relay interrupter arrangement. The switch S is then mechanically coupled with the make and break switch Si in order to permit a changeover from one modulation frequency to another at the same time as the keying rhythm is changed. The possibility for a change with respect to the keying frequency and to the frequency of modulation involves the advantage that the same transmitting system may arbitrarily be utilized for difierent purposes, for example, as a first or second pre-signal emitter in radio beacon arrangements for landing airplanes.

The voltage which is utilized for the energization of the relay interrupter arrangement itself and which is supplied by the battery B of Fig. 2, is suitably derived from the main supply portion .of the transmitter and rectified in the rectifying device R which may comprise dry rectifiers, for example.

The windings of the relays I, II and III are connected in different circuits and in parallel with one another and parallel to the terminals of a potential source, -e. g. in parallel to the rectifier R. The contact I of relay I forms part The switch S enables. a changeover from one keying frequency to anof the circuit in which the windingof relay II is included. The contact 2 of relay IL-forms" relay II is included in the circuit of the low fre-' quency generator F for the purpose of keying the transmitter. It will be assumed that the switch S is closed and that all relays are connected in circuit. The system then operates as follows:

When the. switch A is .closed the circuit for relay I is likewise closed so that this relay is energized and closes its contact I so as to energize relay II. This relay reverts its contact 2 with the result that relay-III is energized, while its contact 2'- is opened so as. to interrupt the modulation circuit of-the transmitter. The relay I is de-energized in response to the tilted contact 2. This relay releases with delay and opens its contacts I whereupon the relay II likewise releases with delay thus opening its contact 2 and closing its contact 2' which latter contact closes the modulation circuit of the transmitter so that a new signal commences. The previously energized relay III opens-its contact 3 and this contact is not closed before relay lII releases and reverts its contact 2. Signals as shown in Fig. lb are then transmitted. 1 When switch S is moved to its open position the relay III is ineffective so that signals of shorter. duralength and frequency comprising a plurality of circuits arranged in parallel with one another and in series to a current source, a plurality of relays each having its winding connected-in the appertaining circuit, contacts controlledby each of said relays arranged in a corresponding circuit with a winding of another of saidrelays to render said relays'alternately effective, and means operatively associated with each relay for determining the attraction and the release time of said relay. Y T

2. An arrangement according to claim 1 comprising means for arbitrarily rendering a number of said relays efiective or ineffective to select a desired keying frequency, and means for simultaneously selecting a predetermined appertaining modulation frequency.

3. An arrangement according. to claim 1, in which said relays are equally or differently timed, comprising means for arbitrarily rendering a number of said relays effective or ineffective to select a desired keying frequency, means for simultaneously selecting a predetermined appertaining modulation frequency, and means connecting said arrangement to a directional radio beacon transmitting system;

4. An arrangement according to claim 1, further comprising means for arbitrarily rendering a selected number of said relays efiective or ineffective.

ERICH STUTIUS. 

